The invention is related to a drum brake type electric parking brake apparatus that expands a gap between a pair of brake shoes to generate a braking force by an electric motor. Specifically, the invention is related to a drum brake type electric parking brake apparatus capable of realizing a structure that can suppress the number of parts thereof, thereby reducing the cost of the apparatus.
In addition, the drum brake type electric parking brake apparatus that is the subject of the invention includes not only a structure in which a drum brake is used for both a service brake for decelerating or stopping a vehicle from a traveling state and a parking brake for keeping a stopped state but also a drum-in disc brake in which a disc brake is used for the service brake and only a drum brake is used for the parking brake.
A parking brake apparatus that keeps a vehicle at a stopped state without pressing a brake pedal is embedded in a drum brake. Also, a parking brake operation is also mechanically (non-hydraulically) performed through a force-multiplication mechanism such as link mechanism in which an electric motor is used as a drive source (for example, Patent Documents 1 and 2), which is implemented in some vehicles. For example, Patent Document 1 discloses a structure in which a hydraulic disc brake is used as a service brake and a mechanical drum brake having an electric motor as a drive source is used as a parking brake.
The drum brake type electric parking brake apparatus disclosed in Patent Documents 1 and 2 expands a gap of a pair of brake shoes, which is supported to an outer-side surface of a backing plate so that the backing plate can be displaced in a radial direction, by an electric actuator unit. The electric actuator unit is configured by a combination of an electric motor and a decelerator and expands a gap between one end portions of both brake shoes in a circumferential direction by a force-multiplication mechanism such as link mechanism, based on activation of the electric motor.
In the drum brake type electric parking brake apparatus that has been conventionally known, including the structures disclosed in Patent Documents 1 and 2, the electric actuator unit is supported and fixed to the backing plate. The backing plate is coupled and fixed to a knuckle consisting of a suspension with the electric actuator unit being fixed. Therefore, regarding the knuckle, a knuckle having a shape capable of preventing an interference with the electric actuator unit and coupling and fixing the backing plate should be used. Since the knuckle having the shape is special and a dedicated member should be thus newly made, the cost is inevitably increased regarding the mounting of the drum brake type electric parking brake apparatus.
In addition Patent Document 3 also discloses a structure that relates to the implementation of the invention, in addition to Patent Documents 1 and 2.
[Patent Document 1] JP-A-2001-504417
[Patent Document 2] JP-A-2011-099458
[Patent Document 3] JP-A-10-325429